Commercially available web fed rotary printing presses typically include printing units arranged at fixed locations in the pressroom. After the web has moved through the printing units, it is transported to folder and cutter units that fold the web and cut the web lengthwise and crosswise into printed products, such as signatures used to create newspapers, magazines, and the like. The web is cut into signatures that are typically conveyed to a fan or other delivery system, which deposits them on, for example, a conveyor belt. The printing press can be configured so that signatures are evenly diverted among several fans or other delivery systems using a diverter mechanism, including mechanical cam-driven flipper diverters or mechanical eccentric lobe diverters.
A conventional mechanical cam-type diverter 10 is illustrated in FIG. 1 having a shaft 15 and a plurality of diverters 20 mounted thereon. Such diverters typically require torsion springs to pre-load a cam follower 25 against a surface 30 of a rotating cam 40 and maintain surface contact through the action of cam 40. The torsion bar 35 preload must be set high enough so that cam follower 25 does not lift off the cam surface 30 at the maximum operating speed requirement of the diverter 10. Since the torsion bar 35 preload adjustment is a manual setting, the preload is always present in the torsion bar 35, even when the diverter 10 is not operating. Since the high preload is always present, the cam follower 25 and cam surface 30 are always subjected to high preload stresses that can prematurely wear the cam surface 30 and reduce the life of cam follower 25. This high preload force also requires the mechanical assembly supporting the diverter shaft 15 and torsion bar 35 to be sufficiently strong and stiff to prevent vibration and/or deformation under normal operation. Another limitation of this design is that the cam action angles are fixed and therefore cannot be adjusted to take advantage of smaller product lengths and the increased spaces between them. Furthermore, the number of cam actions controlling the diverter shaft 15 is fixed at the time of design and is therefore impossible to vary once the cam 40 is manufactured. So if the cam 40 has one rise action and one fall action, the diverter shaft 15 will be limited to this particular characteristic for the life of the cam and such characteristics may only be changed by changing the cam. Finally, since the cam 40 forces the diverter shaft 15 to oscillate through a relatively small angle of rotation, there is a risk of premature bearing failure of the bearings for diverter shaft 15 due to uneven stresses on the bearings.